Vitrification is preferably used in the treatment of radioactive wastes. Vitrification of radioactive wastes is a process in which the nuclear species of radioactive wastes are bonded into a glass matrix, so that the vitrification can realize stabilized treatment of the radioactive wastes.
To vitrify radioactive wastes, the radioactive wastes are put into a glass melting furnace together with fragmented glass so that the radioactive wastes are melted with the glass, thus forming glass melt in the furnace. When solidifying the glass melt, solidified glass that captures the nuclear species of radioactive wastes therein is produced.
A conventional temperature measuring apparatus used to measure the temperature of the glass melting furnace is a thermocouple as disclosed in Korean Patent Application Publication No. 10-2010-0126922. Here, the thermocouple performs the measurement of temperature while being in direct contact with an object to be measured, so that a protective pipe surrounding the thermocouple is exposed to high temperature glass melt and is subjected to chemical corrosion. The chemical corrosion of the protective pipe reduces the life span of the protective pipe, and it is required to frequently change the protective pipe with a new one.